Hard disk drives generally incorporate stacked, commonly rotated rigid magnetic disks which are used for storage of data in magnetic form on the disk surfaces. The data is recorded in concentric, radially spaced data information tracks arrayed on the surfaces of the disks. Transducer heads are driven in a path toward and away from the drive axis in order to write data to the disks and read data from them.
The hard disks used in hard drives can comprise a substrate plated, for example, with nickel and phosphorus. Subsequent to plating, the disks are usually polished using chemical mechanical polishing, which exposes the disk to contaminants from the polish slurry, polish residue, manufacturing equipment, and/or the manufacturing environment. Nickel and phosphorus in the polishing slurry and/or derived from the surface of the disk, for instance, may bond back to the disk surface.
Contaminating particles on the surface of a hard disk, in particular nickel oxide (NiO) and nickel phosphorous (NiP) particles, can cause thermal asperities, i.e. local heating of the disk during operation due to the mechanical collision of the drive head with such particles protruding on the disk surface. If contaminating particles are not removed from the plated and polished disk, the operation and performance of a hard drive incorporating the disk may be negatively impacted, for instance due to head crash.